In spite of the growing interest in essential oils (EOs) and their commercial importance, it is not yet clear how development factors influence the plant material optimum harvesting period for EOs production. factors that determine the EOs' composition and yield are numerous, and in some cases, it is quite difficult to isolate them as many are interdependent and influenced by each other. Therefore, EOs chemical composition is subject to high quantitative and qualitative variations, as well as their related biological activities or properties.